Track circuits in railroad tracks are used to control signals for trains and detect broken rails. Railroad rails are utilized in these circuits as electrically conductive elements and they transmit low-voltage electrical current until terminated by an electrical insulator. Insulated rail joints are used to block transmission of this electrical current in the rail without disturbing the structural continuity or integrity of the rail.
Typical track circuits work with the principle of train wheels and axles making an electrical connection between two parallel rails that are electrically separated otherwise and shunting the tracks, thence de-energizing the signal relay system, thence dictating the color of the signal light (red, green etc).
Insulated rail joints are used at the ends of track circuits to electrically block out a section of a railroad track. The main design principle of insulated rail joints is to maintain railroad tracks structural integrity while creating an electrically insulating gap in a railroad rail. This is commonly accomplished by gluing and bolting two insulated rail joint bars to a rail with insulating bushings around the bolts and using a insulating piece about 0.25 inch in thickness matching the shape of the cross section of rails between the two rails. There are various insulated joint designs and some of them do not incorporate an adhesive.
Low-voltage electrical power source and signal relay system need to be physically and electrically connected to the rail where insulated rail joints are located. These connections (a.k.a. rail bonds) are carried out by either drilling the rail and inserting the electrical connector through this hole or welding electrically conductive tabs on the rail. Furthermore, usually more than one connection is needed during the life-cycle of an insulated rail joint in track, hence field maintenance crews weld tabs or drill rails in the operational environment where high quality control measures may not be always achievable. Attachment of rail bonds to rails should minimize damage to the rail, as every damage to the rail is a safety risk. Additional considerations for rail bond attachment are low resistance, long fatigue life, accommodation of normal rail movements, certainty to fail in abnormal rail movements, facility of installation, and facility of inspection and maintenance. Various clamping and force fit connecting devices have been used in holes bored in the rail sections. These sometimes result in an unsatisfactory physical rail connection and breakdowns are caused by rail vibration, the adverse effects of inclement weather, etc. When welding or brazing of numerous bond wires to rails is used heating of the rail inherent in the welding process may cause flaws in the rail, making the rail more likely to fail or break. Further limitations and disadvantages of conventional and traditional approaches will become apparent to one of skill in the art through comparison of such systems with the present disclosure as set forth in the remainder of the present application with reference to the drawings.